Grinder



Feb. 81, 19449 J. G. ZUMMACH GRINDER Filed July 14, 1941 5 Sheets+$heet 1 INVENTOR Feb. 8, 1944. J. G. ZUMMACH GRINDER Filed July '14, 1941 3 Sheets-Sheet 2 lllllllllll II! a AITORNE Fkb.8,1944.

J. G. ZUMMACH GRINDER Filed July 14, 1941 a Sheets-Sheet s ATTORNE Patented Feb. 8, 1944 UNITED STATES PATENT OFFICE GRINDER John G. Zummach, Racine, Wis. Application July 14, 1941, Serial No. 402,326

7 Claims. (01. 51-140) This invention relates to grinders and is particularly directed to grinders for sharpening knives, cleavers, or other instruments of this general nature.

Objects of this invention are to provide a power driven grinder which is so made that it will sharpen both sides of a knife or cleaver or other device simultaneously as the knife or cleaver is drawn through the apparatus.

Further objects are to provide a grinder in which the inclusive angle between the two sides of the knife can be adjusted so that for fine knives a very small inclusive angle can be had and for cleavers, or other devices of this nature, a greater inclusive angle may be obtained.

Further objects are to provide a grinder in which the grinding means is so made that grinding agents are positioned on opposite sides of the knife or other device and are arranged to operate through a path or zone which intersects, that is to say, one of the grinding agents crosses the center line of the knife from one side thereof during its grinding operation and the other grinding agent crosses the center line of the knife from the other side thereof during its grinding operation.

Further objects are to provide a grinder which is so made that it will'not leave a wire edge on the knife but which instead completely removes any wire edge during the grinding operation so that when the knife is finally withdrawn from the grinder, it is in condition 'for immediate use.

Further objects are to provide a device which is compact and is self-contained and is a unitary structure so that it may be placed on a counter or other support and which may be readily used by an unskilled operator, and which is rapid in its operation.

Embodiments of the invention are shown in the accompanying drawings, in which:

Figure 1 is a front view of one form of the device with the front plate removed and with a part broken away.

Figure 2 is a sectional view on the line 2--2 of Figure 1.

Figure 3 is a sectional view on the line 3-3 of Figure 2.

Figure 4 is a diagrammatic view, approxi mately on the line 4-4 of Figure 2, showing the arrangement of the gears.

Figure 5 is a sectional view on the 1ine5-5 of Figure 1.

Figure 6 is a sectional view on the line 3-45 of Figure 1.

Figure 7 is a fragmentary View with the front plate removed and with parts broken away showing a further form of the invention.

Figure 8 is a sectional view on the line 8-8 of Figure 7. v

The form of the invention shown in Figures 1 to 6 is provided with a bed plate I which carries a shell like head 2 provided with a gear compartment 3 and a grinding compartment 4. These compartments are closed, respectively, by means of a rear plate 5 and a front plate 6. The front and rear plates are slotted, as well as the central partition I, to receive a knife and rollers are provided on which the knife is adapted to rest. These rollers are indicated at 8 in Figures 1 and 2. If desired, these rollers may be formed of two cone sections in each instance.

The driving motor is indicated at 9 and is carried by the base I and its driving shaft is provided with a driving gear I 0 meshing with a gear II on the shaft l2 of the lower right-hand pulley l3 for the right-hand abrasive belt I 4. The shaft I2 is provided with a gear [5 which meshes with a gear l6, see Figure 4, carried by the shaft ll of the left-hand pulley [8 for the left-hand abrasive belt 19, see Figure 1.

The right. and left-hand abrasive belts extend over upper pulleys 20 and 2| respectively. These pulleys are carried by shafts 22 and 23, see Figures 3 and 6. The shafts 22 and 23 are rigidly carried by pivotally mounted arms 24 and 25 which have meshing gear segments indicated at 26 in Figure 3 so that when one arm is rocked, the other is simultaneously rocked to a corresponding amount. The shafts 22 and '23 extend through slotted openings in the intermediate partition 1.

An adjusting and locking thumb screw 21, see Figures 1 and 3, is provided whose shank extends through a slot 28 in the casing or head 2 so that the thumb nut may be loosened and the arms 22 and 23 may be adjusted, the thumb screw thereafter being tightened to lock the arms in their adjusted position. This adjustment moves the pulleys 20 and 21 towards or from each other to thereby increase or decrease the inclusive angle between the two faces of the knife.

The belts are caused to alternately cross the center line from opposite sides of the knife during the operation of the apparatus. This is accomplished by providing cam pulleys 29 and 3|] which are mounted on shafts 3| and 32 respectively, see Figures 1 and 4. These shafts are operatively coupled together by means of gears 33 and 34 and the gear 33 is driven from the gear 15 by means of an idler gear 35, see Figure 4,

The cam pulleys 23 and 33, see Figure l, are so related to each other that when one of the pulleys projects its belt across the center line, the other pulley allows its belt to move out of the way so that the belts are alternately caused to cross the center line during the operation of the apparatus to thereby-sharpen the knife from each side thereof and to form an angle between the two faces of the knife, which angle may be made relatively great, as for instance when a cleaver is to be sharpened, or may be relatively small when a finer type of knife is employed by adjusting the thumb screw 21 as previously described.

The arms 24 and 25, see Figure 3, are pivotally mounted to rock about the axis of the shafts 3| and 32. I

Belt tightening means are provided which may comprise a pair of arms 36 and 31, see Figure 3, which are pivotally mounted to rock about the axis of the shafts I 2 and H respectively. These arms are urged downwardly by means of springs 38. The arms rigidly carry shafts 39 and 66 respectively on which are mounted idler pulleys 4i and 42, see Figure 1. The shafts 39 and 36 project through slots formed in the central partition l.

The belts M and I9 are abrasive belts having the desired grinding characteristics and the suitable size of grit or other abrasive material. They are driven so that their adjacent sections, see Figure 1, travel downwardly and thus sharpen the knife on opposite sides thereof by a downward stroke, and as the belts are alternately caused to cross the center line as previously described, it is obvious that first one belt and then the other crosses the center line and. thus removes any wire edge that might be formed on the knife. Also it is apparent that the knife may be drawn through the device without any thought on the part of the operator and with the assurance that a good cutting edge will be produced, and that the requisite angle will be maintained between the two faces of the knife.

It is preferable to have the arms '24 and 25 and 36 and 31, see Figure 3, pivotally mounted on the bushings for the shafts 3|, 32, I2 and H, respective, and to have the bushings carried by the central partition 1, see Figure 2, for the respective shafts so that there is not actual hearing engagement between the arms and the respective shafts.

It is obvious also that these bushings as shown could be dispensed with but a better construction is provided by having the arms actually contact the bushings and have the shafts run within the bushings.

In the form of the invention shown in Figures '7 and 8 the abrasive belts are indicated by the reference characters H and 12. These belts extend over the lower pulleys l3 and I4 and over the upper pulleys l5 and 16 respectively. Idler pulleys H and 18 are provided which are carried by pivoted arms 19 and 88 which are pulled by means of the springs 8| and 82 to maintain the belts tight.

Intermediate pulleys 83 and 84 are provided which are carried by a reciprocating frame 85 having a lower cut out portion 86. This cut out portion is engaged on one side thereof by means of the cam 81, see Figure 7, the cam being carried by the driving shaft 88 of the motor or other driving means 89, see Figure 8. A spring 9f] provided for maintaining one side of the cut out 86 in engagement with the cam 81. The pulleys 83 and 84 rotate on stub shafts 9| and 92 which are rigid with the reciprocatory frame 81. These shafts pass through slots 93 and. 94 in the central partition 95, as shown in Figure '7, to guide the frame 81.-

The upper pulleys 15 and 16 may be the drive ing pulleys and may be driven by means of driving belts 96 and 91, one of which is crossed. The belts are driven from the motor shaft 88, as shown in Figure 8.

The guiding rollers for the knife are indicated at 98 in Figure '7 and the casing is slotted so that the knife may be drawn through th casing during the sharpening operation. It is apparent that in the operation of the apparatus the reciprocatory member is oscillated back and forth to'thereby cause first one and then the other of the abrasive belts H and 12 to cross the center line and thus grind opposite faces of the knife at anangle to each other.

It will be seen that novel forms of grinding devices have been provided in which the article to be sharpened is ground from opposite sides thereof to the exact angle desired, and which is so made that no skill is required on the part of the operator, the operator merely drawing the knifethrough the device with the assurance that the correct grinding edge will be produced.

It is to be noted that in both forms of the invention that the grinding means yieldingly engages the knife from opposite sides thereof, as the belts are guided and supported at points spaced from the knife so that there is an immediate yield of the belts at the point where they engage the knife. In view of the fact that there is scarcely anyinertia for this small portion of the grinding belts, these grinding belts will substantially instantly yield at these points and thus a very keen and uniform edge is produced.

It wi11 be seen further that each section of the knife is operated on by the grinding means on first one side and then the other in rapid succession. This produces a multitude of alternating strokes from first one side and then the other on every portion of the knife and thus the formation of a wire edge is prevented.

The term knife wherever used in the description or claims is to be interpreted as a generic term for the ordinary type of knife, cleaver, or other cutting instruments of this general order.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

1. A grinder for sharpening knives and the like comprising two abrasive belts, means for driving said belts, guiding means for guiding a knife between said belts, means for moving first one and then the other belt into engagement with opposite sides of the knife, and relatively fixedly positioned guiding means across which the knife may be drawn for guiding the knife in a relatively fixed plane.

2. A grinder for sharpening knives and the likesides of the knife, and relatively fixedly positioned guiding means across which the knife may be drawn for guiding the knife in a relatively fixed plane.

3. A grinder for sharpening knives and the like comprising two abrasive belts having stretches adjacent each other and spaced apart for the reception of a knife therebetween, means for driving said belts, automatically operated means actuated from said driving means for moving said belts alternately into engagement with opposite sides of the knife, belt tightening means for said belts, and relatively fixedly positioned guiding means across which the knife may be drawn for guiding the knife in a relatively fixed plane.

4. A grinder for sharpening knives and the like comprising two abrasive belts spaced apart for the reception of a knife therebetween, means for driving said belts, means for automatically moving said belts alternately into engagement with opposite sides of the knife, and adjusting means for adjusting the angle of said belts with reference to the central plane of the knife.

5. A grinder for sharpening knives and the like comprising two abrasive belts having stretches adjacent each other and spaced apart for the reception of a knife therebetween, power means for driving said belts, guiding means for said belts, means for adjusting the guiding means to vary the angle of said belts with reference to the central plane of a knife, and means for causing said belts to alternately cross the central plane of the knife.

6. A grinder for sharpening knives and the like comprising a unitary structure including a driving motor, a pair of abrasive belts driven therefrom and having juxtaposed stretches between which a knife is adapted to be passed, relatively fixed guiding means for the knife across which the knife may be drawn for guiding the knife in a relatively fixed plane, and automatically acting means driven from said motor for alternately moving the belts laterally into engagement with opposite sides of the knife and causing the belts to cross the central plane of the knife.

7. A grinder for sharpening knives and the like comprising a unitary structure including a driving motor, a pair of abrasive belts driven therefrom and having juxtaposed stretches between which a knife is adapted to be passed, guiding means for the knife, automatically acting means driven from said motor for alternately moving the belts laterally into engagement with opposite sides of the knife and causing the belts to cross the central plane of the knife, casing means enclosing said belts, and externally adjustable means for varying the angularity of the portions of the belts which are moved into engagement with the knife.

JOHN G. ZUMMACH. 

